It’s not just a ubiquitous ad slogan — a primate infant’s access to breast milk has significant consequences for a species’ life cycle. For the first time, researchers have been able to look back 100,000 years to understand how Neanderthal infants might have been nursed and weaned.

According to a study published today in Nature, patterns of barium distribution in the fossilized teeth of a juvenile Neanderthal indicate that the individual began weaning at seven months, comparable to human infants and chimpanzees, but that weaning was completed by the age of 14 months — within the range of human patterns but significantly sooner than chimps.

Weaning, the transitional period between exclusive breastfeeding and a solid food diet, has important implications both for an individual and for the species overall. Early weaning can result in negative health consequences for the infant, but also allows for faster reproduction rates within a population, since females cannot become pregnant while breastfeeding.

Although there is considerable variation in the onset and duration of weaning among different industrial and nonindustrial human societies, researchers found that on average modern human children are weaned at 2.3-2.6 years. Chimpanzees, by comparison, are weaned at an average of 5.3 years.

Researchers hoping to learn more about Neanderthal weaning patterns first studied the distribution of barium in the teeth of human children and captive macaques. As an infant’s teeth develop, daily growth lines in both the crowns and roots leave a record that can be used to determine the individual’s age at various developmental points as well as the teeth’s composition.

Researchers focused on barium levels because the trace element in dental enamel is fairly resistant to breakdown during fossilization.

Inhibited in utero by the placenta, barium levels increase immediately after birth upon the initiation of breastfeeding. The barium/calcium ratio remains high throughout the period of exclusive breastfeeding. When the weaning process begins and solid food is gradually introduced, however, barium levels change markedly, depending on its availability from the plant and animal food sources fed to the infant. When weaned is completed, barium levels return to those seen prenatally.

After verifying how changes in barium distribution corresponded to changes in modern infants’ diets, the study’s authors analyzed the remains of a juvenile Neanderthal found in Belgium’s Scladina cave. Previous, unrelated research using the remains yielded the oldest mitochondrial DNA ever obtained from a Neanderthal — dated to roughly 100,000 years — suggesting the fossil was particularly well-preserved.

They determined that weaning began at seven months and was completed by the age of 14 months. Although it is difficult to draw conclusions about a species’ life cycle from one specimen, this relatively short weaning period suggests that Neanderthals may have had shorter inter-birth intervals than other primates, promoting faster population growth. Researchers plan to study other early hominid teeth in hopes of learning more about weaning patterns in those populations, which will impact our understanding of how those species lived and developed.

…if, in fact, these findings are accurate [relative to other primates, other mammals?] x bodysize, higher growth rates, according to life history theory, MAY indicate that the populations were under stress…that one or more than one factor was perturbing this population…maybe contributing to extinction…
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Maya C

The author’s title and article are extremely misleading. This is very sloppy journalism — the study the author is quoting only used one neanderthal tooth, and indicates no sort of pattern in neanderthal weaning whatsoever. A single case does not translate into a pattern. The science of the barium is interesting, but let’s not make more assumptions about entire races until we have some more facts.

Kathy Dettwyler

Haven’t read the original research article — but do know that the research reported that this Neanderthal baby abruptly stopped getting breast milk at 14 months. Which suggests that his mother died, or some other calamity. Research is clear that around the world, if you don’t count industrialized countries with their cultural patterns of artificially early weaning, children typically nurse from 3-5 years, and longer in the very recent past. And based on other life history variables such as growth, adult body size, age at reproductive maturity, etc., the range for modern humans would be 2.5 to 7 years. If “Neanderthals” as a population stopped nursing at 14 months, that would be well below the modern human biological norm. There are lots of children in industrialized countries who nurse into the 3-5+ year age range as well, so early weaning doesn’t seem to have any biological basis, or long-term history in history in humans. And not to be pedantic, but the term weaning is used in the scholarly literature to mean the END OF breastfeeding, not the transition period. And finally, Neanderthal women, like human women, certainly could have become pregnant again while breastfeeding if they had begun to ovulate again. Lactation/breastfeeding does suppress ovarian function — to different degrees under different circumstances — but to suggest that a mother has to wean to become pregnant again, or can use breastfeeding as a fail-safe contraceptive, is simply incorrect.